MATLAB SIMEVENTS RELEASE NOTES Betriebsanweisung PDF herunterladen (Seite 80)

4 Basic Queues and Servers

4-2

Queues in SimEvents Models

In this section...

“Behavior and Features of Queues” on page 4-2

“Physical Queues and Logical Queues” on page 4-2

“Access Queue Blocks” on page 4-3

Behavior and Features of Queues

In a discrete-event simulation, a queue stores entities for some length of time that cannot

be determined in advance. The queue attempts to output entities as soon as it can, but

its success depends on whether the next block accepts new entities. An everyday example

of a queue is a situation where you stand in a line with other people to wait for someone

(a bank teller, a retail cashier, etc.) to address your needs and you cannot determine in

advance how long you must wait.

Distinguishing features of different queues include

• The queue capacity, which is the number of entities the queue can store

simultaneously

• The queue discipline, which determines which entity departs first if the queue stores

multiple entities

Physical Queues and Logical Queues

In some cases, a queue in a model is similar to an analogous aspect of the real-world

system being modeled. This kind of queue is sometimes called a physical queue. For

example, you might use a queue to represent a sequence of

• People standing in line

• Airplanes waiting to access a runway

• Messages waiting to be sent

• Parts waiting to be assembled in a factory

• Computer programs waiting to be executed

In other cases, a queue in a model does not arise in an obvious way from the real-world

system but instead is included for modeling purposes. This kind of queue is sometimes

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MATLAB SIMEVENTS RELEASE NOTES Betriebsanweisung Seite 80